The present invention relates to a disc drive microactuator, and more particularly to a high resolution head positioning mechanism having one or more piezoelectric elements attached to a slider as a bendable cantilever for selectively moving a head portion of the slider radially with respect to circumferential data tracks of a rotatable disc.
The track density, or radial spacing, between concentric data tracks on magnetic discs continues to increase, requiring greater precision in head positioning. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuator motor, such as a voice coil motor, to position a head on a flexure at the end of the actuator arm. The large-scale motor lacks sufficient resolution and bandwidth to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism is necessary to accommodate the more densely spaced tracks.
One promising design for high resolution head positioning involves employing a high resolution microactuator in addition to the conventional low resolution actuator motor, thereby effecting head positioning through dual-stage actuation. Various microactuator designs have been considered to accomplish high resolution head positioning, including piezoelectric, electromagnetic, electrostatic, capacitive, fluidic, and thermal actuators. Various locations for the microactuator have been suggested, including on the slider, on the gimbal, at the interface between the gimbal and the slider, and on the actuator arm, for example. However, the previous designs all had shortcomings that limited the effectiveness of the microactuator, such as substantial performance limitations or manufacturing complexities, which made the microactuator designs impractical. An effective microactuator design must provide high acceleration in positioning the head while also generating sufficiently large and accurate displacements to precisely move the head across several data tracks on the disc.
There is a need in the art for a microactuator design to provide high resolution head positioning with superior bandwidth performance characteristics that can be implemented by simple and readily available manufacturing processes.
The present invention is a slider assembly for selectively altering a position of a transducing head with respect to a track of a rotatable disc having a plurality of concentric tracks. The slider assembly includes a slider body having a main portion and a head portion separated by a gap. The head portion carries the transducing head. The slider body is arranged to be supported by a support structure over a surface of the rotatable disc. A pair of structural elements are disposed on opposite side surfaces of the slider body between the main portion and the head portion across the gap. At least one of the structural elements is a microactuator responsive to electrical control signals to selectively bend to alter the position of the head portion with respect to the main portion of the slider body. The structural elements are preferably complementary microactuators.
Another aspect of the present invention is a process of forming a pair of microactuators on each of a plurality of sliders. A slider substrate is formed comprising main portions of the sliders, and a sacrificial layer is deposited on the slider substrate. Head portions each carrying a transducing head are then formed on the sacrificial layer. A row of sliders is separated from the slider substrate, an air-bearing surface is formed on each of the sliders in the row, and notches are cut between individual sliders in the row. Microactuators are formed between the main portions and the head portions of the sliders on side surfaces of the sliders in the notches. Alternatively, the microactuator processing may be performed at the wafer level, prior to the steps of separating the slider substrate into rows and defining the air-bearing surfaces of the sliders in the rows. Individual sliders are separated from the slider row such that a pair of microactuators are on opposite side surfaces of each of the sliders. The sacrificial layer is removed to form a gap between the main portions and the head portions of the sliders.
A further aspect of the present invention is a process of forming a microactuator on each of a plurality of sliders. A slider substrate is formed comprising main portions of the sliders, and a sacrificial layer is deposited on the slider substrate. Head portions each carrying a transducing head are then formed on the sacrificial layer. A row of sliders is separated from the slider substrate, and an air-bearing surface is shaped for each of the sliders in the row. Individual sliders are separated from the row of sliders, and a plurality of the individual sliders are glued together to form a slider stack. A plurality of microactuators are formed on side surfaces of each of the sliders in the slider stack, and the sacrificial layer is etched away to form a gap between the main portions and head portions of each of the sliders. The sliders are separated from each other by dissolving the glue. Alternatively, the plurality of microactuators may be separately formed and attached to the side surfaces of the sliders stack, and then separated into individual microactuators for each of the sliders in the slider stack.